Transformers are commonly used in welding type power supplies. Welding type power supply, as used herein, is a power supply that provides a welding type output. Welding type output, as used herein, is an output suitable for welding, plasma cutting, or induction heating. Welding type power supplies have a wide variety of topologies. For example, they can include a preregulator to provide a bus, and have an output converter that converts the bus into a desired current and voltage. Examples of preregulators include boosts, bucks, rectifiers, etc. Examples of output converters, include inverters, boosts, bucks, choppers, etc. Welding type power supplies can have additional, intermediate stages, and can receive utility power as input power, or include a generator.
Many welding type power supplies include an auxiliary power output. This is often provided at 120 volts (or other utility voltages power), and can be derived by transforming input power, or derived from a bus by a converter (such as an inverter). Auxiliary power derived by inverting the bus is also usually transformed (to provide the desired 120V ac). Thus, when auxiliary power is provided, it is common to have an auxiliary power transformer.
Welding type power supplies also generally need control power to power switches, electronics, and processors. Control power is also derived by transforming input power, or derived from a bus by a converter (such as inverter or buck converter). Control power derived by inverting the bus is also usually transformed (to provide the desired control voltages). Thus, it is common to have a control power transformer.
One prior art welding power supply transformer for weld power is described in U.S. Pat. No. 6,864,777, hereby incorporated by reference. Some prior art transformers include a central bobbin having a coil winding window disposed about a central opening in the bobbin. The central opening is provided to receive one or more laminated or ferrite magnetic cores. Standard off-the-shelf magnetic cores are available in a wide variety of sizes and shapes, many of which have square or rectangular cross-sections. The coil windings typically also have rectangular or square cross sections wound close to the magnetic cores. This is because it is generally desirable to keep the coil windings close to the magnetic core to maximize the magnetic coupling between the magnetic core and the coil windings.
Control and auxiliary power transformer windings can be purchased, but is is generally costly to purchase windings. Also, each transformer adds weight and cost to the welding type power supply. Thus, it is desirable to have a reduced number of transformers. Windings and transformers tend to be components that need cooling.
Another problem with welding power supply transformers, is providing adequate insulation between windings, and preventing creepage between windings. leakage inductance.
Thus, it is desirable to provide control and auxiliary power without having separate transformers. Preferably there will be an effective way to cool both the auxiliary and control windings, and there will be adequate insulation and adequate creepage distance between the windings.